Apparatus and method for displaying contour lines and contour line display apparatus

An object of the present invention is to draw contour lines according to specified display coordinates and display the lines immediately. In order to achieve this object, a display rectangular coordinate system and an input rectangular coordinate system that correspond to each other are set up for a display face of a liquid crystal display unit (2) and for an input face of a tablet (6). If an input coordinate is specified on the input face using a predetermined directing device, therefore, a tablet control unit (7) outputs hand-written input coordinate data (step a2) and corresponding display coordinates are specified. Then, a central control unit (15) creates contour data representing contour lines which enclose the figure composed of the specified coordinate data, on the basis of the data according to control of programs (9 to 13) read from a floppy disk (23) and stored in a ROM (8). In other words, the central control unit (15) generates first figure data composed of specified coordinate data (steps a3, a4), then generates second figure data including the first figure data and representing contour lines which enclose the figure composed of the data (steps a5, a6) thereby to create contour data obtained by removing the first figure data from the second figure data (steps b1 to b4). The created contour data is then displayed on the liquid crystal display unit (2) (step b5).